"Don't remember" is equal to "forget" if I understand it correctly. "Don't remember to forget" means "Forget to forget".
Now, the expression 'forget it' is used to emphasize that you're saying 'no' to something:
(Please scroll down to forget it #3.)
So, "Forget to forget" means "I'm saying 'no' to 'to forget'".
It's the same as "Don't forget", isn't it?
Hmm... Forget it!